Shock absorber

Abstract

Provided is a shock absorber in which a check valve seated on a seat portion (second seat portion) having an annular shape is quickly opened during a reverse stroke. As a result, a working fluid in a chamber on a downstream side can be quickly introduced into a back-pressure chamber. Hence, a delay in response of a damping force, which may be caused by sticking of the check valve to a relief valve, can be suppressed.

The invention claimed is: 
     
       1. A shock absorber, comprising:
 a cylinder in which a working fluid is enclosed; 
 a piston, which is slidably inserted into the cylinder, and is configured to partition an inside of the cylinder into two chambers; 
 a piston rod, which is coupled to the piston, and extends to an outside of the cylinder; 
 a passage in which flow of the working fluid is caused by movement of the piston in one direction; 
 a main valve configured to apply a resistance force to flow of the working fluid in the passage from a first chamber of the two chambers, which is the upstream side in the compression stroke of the piston and the downstream side in the extension stroke of the piston, to a second chamber of the two chambers, which is the upstream side in the extension stroke of the piston and the downstream side in the compression stroke of the piston; 
 a back-pressure chamber configured to exert an internal pressure on the main valve in a valve-closing direction of the main valve; 
 a case member having a bottomed cylindrical shape with an opening portion at one end, over which the main valve is arranged, the case member including the back-pressure chamber defined inside; 
 an upstream-side back-pressure introducing passage configured to introduce the working fluid from the first chamber into the back-pressure chamber; and 
 a sub-valve to be seated on a first seat portion formed on an outer portion of the bottom portion of the case member, which is configured to define a first pressure-receiving chamber on an inner side of the first seat portion, the first pressure-receiving chamber communicating with the back-pressure chamber, and to be opened by a pressure in the back-pressure chamber to apply a resistance force to the flow of the working fluid to the second chamber, 
 wherein the first seat portion includes an outer peripheral seat portion extending along an outer peripheral portion of the case member, an inner seat portion arranged on an inner side of the outer peripheral seat portion, and connecting seat portions extending in a radial direction to connect the inner seat portion and ends of the outer peripheral seat portion to each other, 
 the shock absorber further comprising: 
 a downstream-side back-pressure introducing passage defined in the bottom portion of the case member, which is configured to introduce the working fluid from the second chamber with respect to flow of the working fluid, which is caused by movement of the piston in another direction, and is isolated from the first pressure-receiving chamber by the first seat portion; 
 a second seat portion formed on an inner side of the bottom portion of the case member, which is configured to define a second pressure-receiving chamber on an inner side, the second pressure-receiving chamber communicating with the downstream-side back-pressure introducing passage; and 
 a check valve to be seated on the second seat portion, which is allowed to be opened by the working fluid from the downstream-side back-pressure introducing passage, 
 wherein the check valve has a slit extending from an inner periphery-side end portion in a radial direction, and 
 wherein the slit connects the first chamber and the second chamber. 
 
     
     
       2. The shock absorber according to  claim 1 , further comprising first passages configured to bring the back-pressure chamber and the first pressure-receiving chamber into communication with each other,
 wherein the upstream-side back-pressure introducing passage and the downstream-side back-pressure introducing passage are located closer to the piston rod than the first passages. 
 
     
     
       3. The shock absorber according to  claim 2 , wherein the bottom portion of the case member has the back-pressure introducing passage and the first passages. 
     
     
       4. The shock absorber according to  claim 1 , further comprising an elastic sealing member, which is provided at an outer peripheral portion of a surface of the main valve on the back-pressure chamber side, and is configured to seal the back-pressure chamber. 
     
     
       5. The shock absorber according to  claim 4 , wherein the elastic sealing member is integrally and firmly fixed to the main valve. 
     
     
       6. The shock absorber according to  claim 1 , wherein the first seat portion comprises a plurality of arc-shaped portions. 
     
     
       7. A shock absorber, comprising:
 a cylinder in which a working fluid is enclosed; 
 a piston, which is slidably inserted into the cylinder, and is configured to partition an inside of the cylinder into two chambers; 
 a piston rod, which is coupled to the piston, and extends to an outside of the cylinder; 
 a passage in which flow of the working fluid is caused by movement of the piston in one direction; 
 a main valve configured to apply a resistance force to flow of the working fluid in the passage from a first chamber of the two chambers, which is the upstream side in the compression stroke of the piston and the downstream side in the extension stroke of the piston, to a second chamber of the two chambers, which is the upstream side in the extension stroke of the piston and the downstream side in the compression stroke of the piston; 
 a back-pressure chamber configured to exert an internal pressure on the main valve in a valve-closing direction of the main valve, wherein the back-pressure chamber includes an extension-side back-pressure chamber and a compression-side back-pressure chamber; 
 a case member having a bottomed cylindrical shape with an opening portion at one end, over which the main valve is arranged, the case member including the back-pressure chamber defined inside; 
 an upstream-side back-pressure introducing passage configured to introduce the working fluid from the first chamber into the back-pressure chamber; 
 a sub-valve to be seated on an annular first seat portion formed on an outer portion of the bottom portion of the case member, which is configured to define a first pressure-receiving chamber on an inner side of the first seat portion, the first pressure-receiving chamber communicating with the back-pressure chamber, and can be opened by a pressure in the back-pressure chamber to apply a resistance force to the flow of the working fluid to the second chamber, 
 wherein the first seat portion includes an outer peripheral seat portion extending along an outer peripheral portion of the case member, an inner seat portion arranged on an inner side of the outer peripheral seat portion, and connecting seat portions extending in a radial direction to connect the inner seat portion to ends of the outer peripheral seat portion; 
 a common passage configured to bring the extension-side back-pressure chamber and the compression-side back-pressure chamber into communication with each other; and 
 a pilot control valve provided in the common passage, 
 the shock absorber further comprising: 
 a downstream-side back-pressure introducing passage defined in the bottom portion of the case member, which is configured to introduce the working fluid from the chamber of the first and second chambers on the upstream side with respect to flow of the working fluid, which is caused by movement of the piston in another direction, and is isolated from the first pressure-receiving chamber; 
 a second seat portion formed on an inner side of the bottom portion of the case member, which is configured to define a second pressure-receiving chamber on an inner side, the second pressure-receiving chamber communicating with the downstream-side back-pressure introducing passage; and 
 a check valve to be seated on the second seat portion, which is allowed to be opened by the working fluid from the downstream-side back-pressure introducing passage, 
 wherein the check valve has a slit extending from an inner periphery-side end portion in a radial direction, and 
 wherein the slit connects the first chamber and the second chamber. 
 
     
     
       8. The shock absorber according to  claim 7 , further comprising:
 a back-pressure adjustment mechanism configured to adjust back pressures in the extension-side back-pressure chamber and the compression-side back-pressure chamber through a common control valve, 
 wherein the check valve has communication cutouts configured to bring the back-pressure chamber and the common passage into communication with each other. 
 
     
     
       9. The shock absorber according to  claim 7 , wherein the first seat portion comprises a plurality of arc-shaped portions.